I think you'll have to wait for idoru to answer, I've done all what the tutorial said with my Aminet CDs (amiga dats) and they all had same CRC as the ones in TOSEC.I'm not familiar with the CD dumping so can't really help with it.

Detecting gaps shouldn't take anymore than a few seconds to a few minutes most of the time - certainly not anything over 10 mins. It can be a problem on some discs/drives though - both in terms of time (eg. it never finishes detecting) or detecting correct gaps.

You can try Method B or C (the guide does mention this), Method C is usually rubbish though!